Pb3Fe3+2(PO4)4(H2O), a new octahedral-tetrahedral framework structure with double-strand chains
Mills, Stuart J.; Kolitsch, Uwe; Miyawaki, Ritsuro; Hatert, Frédéric Poirier; Kampf, Anthony R.; Matsubara, Satoshi; Tillmanns, Ekkehart
European Journal of Mineralogy Volume 22 Number 4 (2010), p. 595 - 604
published: Aug 1, 2010
ArtNo. ESP147052204013, Price: 29.00 €
A new lead iron(III) hydrated phosphate, Pb3Fe2(PO4)4(H2O), has been synthesised hydrothermally in Teflon-lined stainless steel autoclaves at 220 °C for 7 days, with an initial pH of 1.5. It is the first example of a synthetic hydrous Pb-Fe3+ phosphate. Crystals are small, colourless to white prisms, uniaxial (+) and non-pleochroic. The calculated refractive index for white light is n = 1.95. Single-crystal structure determination (R(F) = 0.0457) shows Pb3Fe2(PO4)4(H2O) to be tetragonal, space group P41212 (no. 92), with a = 9.0440(10), c = 16.766(3) Å, V = 1371.4(3) Å3 and Z = 4. Pb3Fe2(PO4)4(H2O) has a structure type which is based on a tetrahedral-octahedral framework of FeO6 octahedra sharing corners with PO4 tetrahedra, with Pb atoms and H2O molecules occupying voids in the framework. Pb3Fe2(PO4)4(H2O) is homeotypic with synthetic Pb3Cr2(PO4)4; both compounds share the same heteropolyhedral topology and the same space group, but only Pb3Fe2(PO4)4(H2O) contains an additional position occupied by a water molecule. The octahedral-tetrahedral chain of Pb3Fe2(PO4)4(H2O) is topologically similar to double-strand chains found in the structures of hannayite, galliskiite, kapundaite, PbIn(AsO4)(AsO3OH) and Na2.88Fe(PO4)2. Infrared spectroscopy is used to describe the vibrational properties of Pb3Fe2(PO4)4(H2O).